1. Field of the Invention
The invention relates to a stabilization device for stabilizing vertebrae or bones that includes a bone anchoring device and at least two stabilization rods having different diameters.
2. Description of Related Art
For stabilizing the spinal column, bone anchoring devices are known that include a shaft to be anchored in bone and a head to be connected to a rod. Usually, a rod connects several bone anchoring devices. Depending on the medical condition and the region of the spine that is to be stabilized, rods with different diameters may be required. The diameters of the rods range from 3 mm to more than 6 mm. Generally, the diameter of the rods used in the lower part of the spine is larger than the diameter of the rods used in the upper part of the spine. For example, in the cervical-thoracic region of the spine, rods with a diameter of 3 mm to 3.5 mm may be used, in the transitional zones between the cervical-thoracic and the thoracic-lumbar region, rods with a diameter of 3.5 mm to 4.5 mm may be used, in the thoracic-lumbar region, rods of usually 4.5 mm to 5.5 mm may be used, and in the lumbar-sacral region, rods with a diameter of 5 mm to 6.35 mm may be utilized.
For each rod of a certain diameter, specific bone anchoring devices, such as pedicle screws, are required. They differ from each other in particular by the size of the recess into which the rod is inserted. The need for these different bone anchoring devices increases costs and renders spinal surgery more complicated for a surgeon or practitioner.
U.S. Pat. No. 5,873,878 discloses an anchoring member for attachment to a vertebra and for use with a first rod having a first diameter and a second rod having a second, smaller diameter. The anchoring member includes an insert member which can be inserted into the head of the anchoring member so as to allow the insertion of a rod with a smaller diameter.
EP 2 070 485 A1 describes a monoaxial bone anchoring device and a polyaxial bone anchoring device each of which can be used with rods of different diameters.